The present invention relates to a still video signal playback apparatus.
A still video signal of an image shot by use of a camera such as a still video camera, or a still video signal supplied from a television system, is magnetically recorded on a video floppy disk such that a field of still video signals are written on each track of the floppy disk. A recording manner in which a field of video signals are recorded for each image is called a field recording, whereas a recording operation in which two fields (i.e. one frame) of video signals are written in two tracks for recording an image is caed a frame recording.
In the color system of the National Television Systems Committee (NTSC), a screen image (or one frame) is produced through an interlaced scanning effected on two-field signals. In a case of a frame recording, since two fields of video signals are recorded, there does not arise any particular trouble; however, for a still video signal processed in the field recording operation, it is necessary to convert the signal into a signal suitable for the interlaced scanning for the playback and display thereof. This signal conversion is effected by a field/frame conversion circuit. A signal read from a video floppy disk is used as a first (or second}field signal, whereas a second (or a first) field signal is produced by delaying 0.5H (H stands for a horizontal scanning period) the signal read from the video floppy disk in the conversion circuit above.
In the interlaced playback operation of the field signal described above, on horizontal scanning lines where the first and second fields are adjacent to each other, there appears an image associated with the same video signal, which causes the playback image to be shifted upward and downward in some cases. To overcome this difficulty, there has been employed a method in which in one of the fields, an image of each horizontal scanning line is represented with a video signal which is attained as an arithmetic means of a video signal associated with the horizontal scanning line and a video signal related to a preceding horizonal scanning line previous thereto.
On the other hand, in a still video signal playback apparatus, there are disposed various circuits for improving the quality of the visualized playback image such as a noise cancel circuit to remove a high-frequency noise signal contained in the video signal and a drop-out compensator circuit to compensate for a space or blank portion appearing in the screen when a portion of the video signal is lost (i.e. a drop-out takes place) because of, for example, a recording failure or a read error.